The present invention relates to a sheet feed device installed in a copier, a printer or like recording apparatus for feeding sheets one at a time and, more particularly, to a sheet feed device capable of allowing sheets to be fed selectively in an automatic and a manual modes.
Prior art sheet feed devices of the type described include a one which is made up of sheet feed means for sequentially picking up and feeding a stack of sheets which are, for example, loaded in a sheet cassette at a sheet loading section, an arm operatively connected to a driver, which includes a DC motor, to push the sheet cassette upwardly from a standby position to a sheet feed position, and a manual insertion tray movable between an operative position adjacent to the sheet feed means and an inoperative position remote from the operative position.
In a sheet feed device having the above construction, in an automatic sheet feed mode, the manual insertion tray is held in the inoperative position so as not to interfere with the operation. In a manual insertion mode, on the other hand, the operator may move the tray to the operative position from the inoperative one. At this instance, since the sheet stack in the sheet cassette is in contact with pick-up rollers of the sheet feed means, the sheet cassette needs to be lowered, or returned, away from the pick-up rollers. In the prior art sheet feed device, while the manual insertion tray is moved to the operative position, the sheet feed cassette is mechanically lowered. Specifically, the driver includes transmission means which is adapted to transmit the rotation of the DC motor to the pusher arm and implemented by a gear mechanism; when the manual insertion tray is moved, it cancels meshing of a part of the gear mechanism via a plurality of lever members while stretching a spring adapted to ensure the meshing.
The problem with such a mechanical cassette lowering scheme is that every time the manual insertion tray is moved from the inoperative position toward the operative position and vice versa, annoying metallic noise is produced at and near the lever members and others. Another problem is that there is an increase in the required number of structural elements and, therefore, the cost is considerable.
Further, the manual insertion tray is mounted rotatably and detachably to a copier or like recording apparatus. This, coupled with the fact that the center of rotation of the tray is located above the pickup rollers of the sheet feed means, the rotatable section inclusive of the tray occupies a substantial space and, thereby, limits the allowable overall length of the tray.